Madrid — The coronation of Spain's soon-to-be King Felipe VI is now all but assured, after the Spanish Senate today approved legislation to enable his father's abdication.

But despite the surety of his future crowning, Prince Felipe is getting a lukewarm welcome from many Spaniards – even some who support him and his father, the abdicating King Juan Carlos – who hold mixed feelings about the monarchy and its future in Spanish society.

Politically, the prince's coronation is certain. Since Juan Carlos announced his surprise abdication on June 2, Spain's mainstream parties have solidly backed the ongoing political and institutional preparations for Felipe's direct succession.

Last Wednesday, Spain's lower house of parliament overwhelmingly voted to pass legislation enabling his ascent: 299 voted in favor, with 19 against and 23 abstentions. And today, the Spanish Senate moved the legislation along behind a 233 to 5 vote (with 20 abstentions), clearing the path for Juan Carlos to sanction the law executing his abdication on Wednesday.

And so on Thursday, barring unforeseen circumstances, a joint session of parliament will proclaim Felipe the new king of Spain, followed by a swearing-in ceremony and a public address from the new monarch. (King Juan Carlos will not attend the parliamentary ceremony, reportedly to avoid drawing attention from the new king.)

But Spanish public's support for the monarchy is not nearly so uniform as its parliament's. Although many still support the crown, tens of thousands of Spaniards have marched over the past two weekends against Felipe's direct succession.

The crown has been directly tied to Spain’s cohesion and identity for centuries, for better or worse depending on whom you ask.

The monarchy was abolished in 1931 after republican parties swept to power. But the new republic was short-lived, ending in 1939 after the government was defeated by Gen. Francisco Franco’s fascist forces in the Spanish Civil War. Before his death in 1975, General Franco reinstated the monarchy to succeed him, with Juan Carlos wearing the crown.

This lack of continuity over the last century may have sapped some of the public's support for the monarchy. Juan Carlos is generally well regarded by Spaniards, as he is credited for holding Spain together and overseeing its post-Franco democratic transition. But the loyalty of many is to the man, not the institution.

According to a recent Metroscopia poll published in Spain's main daily El País, almost half of Spaniards said they would support the succession of Felipe to the throne of Spain. Another 36 percent said they want the monarchy abolished, and 15 percent are undecided.

Indeed, even if most Spaniards support Felipe’s ascension, 62 percent of all Spaniards also want a referendum at some point in time to decide whether Spain should abolish the monarchy. And of people aged under 34, more prefer a republic to a King Felipe VI, and three-quarters support a public referendum on the monarchy – suggesting the institution has an eventual expiration date.

According to the poll, the typical anti-monarchist is a young, ideologically left-wing individual, in favor of bringing back the republic that ended in 1939. And a big reason for anti-monarchists' opposition is their long-held aspirations to secede from Spain. They see the monarchy as one and the same with the centralized government they want to escape.

Currently, a referendum is not a possibility. It would require a lengthy constitutional reform that has been ruled out by the government.

But even with Felipe's rise to the throne all but guaranteed, it looks like Spain's long-dormant anti-monarchic roots – particularly among the young population who will make up the core of his subjects during his reign – may prove a challenge to his position in the future.